How old are your bulbs? If they are older then they may have reached the end of their life span and it's time to replace them. If they are young bulbs it's possible they just aren't big enough to produce flowers yet. Leave teh ;eave alone until they die back naturally so that they feed the bulb for next year.

LynAB, Zone 3A----------------------------------“Those who say it can't be done are usually interrupted by others doing it.” ` James Arthur Baldwin"